Immanuel Kant’s conception of perpetual peace took into account the propositions already developed by l’Abbé de Saint-Pierre and Rousseau while exploring new routes leading to the end of all possible conflicts between so-called “civilised nations”. His preoccupation with the subject was mooted in his early writings of the 1750’s and 60’s before finding a theoretical formulation in his ‘Idea for a Universal History with a Cosmopolitan Purpose’ in 1784 and his treatise ‘Perpetual Peace: A Philosophical Sketch’, published in 1795 at the height of the new conflicts generated by the threat of the French Revolution in Europe. 

Despite his unconditional support for the republican ideals furthered by the French revolutionaries, the Königsberg philosopher was strongly guided by his Pietist education in his moral reflections on the nature of international relations. A pacifist at heart, Kant’s judgment was significantly  informed by his reading of Rousseau’s writings. He identified three paramount conditions for attaining an enduring peace between nations: firstly, a stable political situation prevailing in every one of the countries prepared to enter into a lasting alliance of non-aggression. Secondly, a genuine union of sovereign nations motivated by mutual commercial interests instead of empty dreams of territorial aggression and conquest. Lastly and most importantly for Kant, the notion of peace had to be inculcated in every citizen and the best way to achieve such a noble end was to establish republican forms of government worldwide. 

Democracy, firmly rooted in the ‘public use of reason’, appeared like the ultimate deterrent against war-mongering monarchies, permanently vying for military supremacy in the name of vainglorious prestige. By spreading the republican ‘gospel’, Kant was convinced that he was promoting a message of peace and paving the way to a future collaboration between previous ennemies. Although he would have condemned the imposition of a republican regime on any reluctant nation, he clearly indicated that a defeated ‘unjust enemy’ may be put back on the righteous path by being requested ‘to adopt a new constitution that by its nature will be unfavourable to the inclination for war.’ 

Besides, Kant considered the duty of every wealthy state to help poorer nations in their struggle to eliminate poverty and provide education for its citizens. By removing all major obstacles to the full exercise of personal autonomy, he was convinced that political progress could be achieved and thus the cause of peace greatly enhanced. He wished for the abolition ‘in time’ of standing armies. In his ‘Secret Article relating to Perpetual Peace’ (Second Supplement), he expected philosophers to play a central role in instructing citizens about the blessings of peace:

‘The maxims of the philosophers regarding the conditions of the possibility of a public peace, shall be taken into consideration by the States that are armed for war … That ‘kings will philosophise or philosophers become kings’, is not to be expected. Nor indeed is it to be desired, because the possession of power inevitably corrupts the free judgment of reason. But kings or king-like nations, who govern themselves according to laws of equality, should not allow the philosophers as a class to disappear, or to be silenced; rather should they be allowed to speak forth their maxims publicly.’